I had an image that was kind of blah in plan ole B&W and looked about the same on Ilford MGFB Classic as it did on MGFBWT. Kind of a flat grey. I had changed the tones in Photoshop to see how it would look in warmer tones and liked the results. So I bought some selenium and set to work.

My initial dilution was 1:9 chosen for the slow change of tone so I could see it.
I tested several scraps of WT paper from 1 minute to 20 minutes . The 5 minute test definitely had a warmer and more contrasty hue but was not "brown".
From the test I knew I could get full toning of the print by 15 minutes.
At about the 7 minute mark the warmtone paper started a noticeable color shift in the dark zones. By 12 minutes the entire print was a nice chocolate brown in the dark and mid tones.
I then changed my dilution to 1:6 to see if there was any noticeable color difference on the warmtone paper but there was not, it just finished faster. Began shift at 4 minute mark.

And since I had the same image using MGFB Classic I put it in the toner. A scrap revealed a very different color hue, more purple-ish when wet at the 5 minute mark in the darker tones.
I put in a whole print and pulled it at 15 mins.

Here is a sample of the before and afters. Note the Classic and Warmtone papers are virtually the same untoned.
Click image for larger version. 

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